A variety of approaches have been developed for administering a biologically active agent to a patient in a continuous or sustained manner. However, currently available approaches often involve disadvantages or limitations.
In many conventional controlled release systems, the active agents are incorporated into solid, monolithic polymeric matrices. The matrices are hard, unpliable and when surgically implanted into patients' bodies, cannot be molded to conform to the shape of the implant pocket. Often, the sizes and shapes of the matrices and the surgical implantation lead to patient discomfort and complications. In recent years, injectable systems such as polymer solutions and dispersions of microparticles have been developed to overcome these problems. The injectable systems incorporating polymer solutions, however, depend upon the transformation phenomenon associated with the insoluble polymer and aqueous based body fluid. If there is a low quantity of available aqueous fluid at the implant site or the injectable system does not permit substantial influx of water, it does not transform within a reasonable time.
Therefore, development of a surgically implantable solid implant that is moldable and shapable for easy placement and adaptation to the implant site, but then becomes hard and rigid after implantation in the body.